The invention is directed to a method for manufacturing ropes, cables or the like, whereby an envelope of a flexible, web-shaped material, for example paper, is produced around at least one central core, for example a conductor, moved in the direction of its longitudinal axis, and the structure that has arisen in this way is stranded in a traditional way while being moved, for example with a SZ stranding, whereby at least one further layer of plastic material can also be applied onto the moving, stranded structure in any case, preferably by extrusion; the invention is also directed to an apparatus for the implementation of the method, i.e. for the manufacture of ropes, cables or the like, comprising a means for moving a central core, for example a conductor, in the direction of its longitudinal axis, delivery means for a flexible, web-shaped material, for example paper, in the immediate proximity of the moving core and parallel thereto, and comprising at least one following guide means for forming a closed envelope of the web-shaped material around the core, as well as a stranding mechanism, for example an SZ stranding mechanism, and, in any case, also at least one extrusion means for applying a further layer of plastic material onto the moving, stranded structure.
There are many applications wherein a rope, a cable or the like must be manufactured in such a way that an envelope is produced around the central core by stranding, whereby an intermediate layer composed of a thin, typically web-shaped material is also provided between this core and the envelope. For instance, the ground conductor in electrical cables is often wrapped with paper, after which the stranding occurs. This can ensue, for example, with the method of SZ stranding, whereby the conductors are conducted through a perforated disk with rapidly changing rotational sense, so that the drums for the fibers of the envelope need not be moved around the central core. There are, however, other methods where this occurs and that thereby produce a stranding with only one rotational sense. In order to then apply the intermediate layer of paper onto the central core or, respectively, the conductor, it has already been proposed to wrap a paper strip around the core oriented obliquely relative to the longitudinal axis of the cable; this, however, causes particular difficulties given extremely high-speed systems. Paper strips that are supplied in longitudinal direction and run with the speed of the cable have likewise been disclosed, these being folded once in length and around the central core. It is thereby disadvantageous that this envelope is not symmetrical around the longitudinal axis of the cable and is also open at one side, so that problems relating to the complete covering of the core derive over and over again, specifically in high-speed systems.
An object of the present invention was therefore to improve a method of the type initially cited such that, while avoiding the above-described disadvantages and problems of the prior art, a complete and dependable envelope of a central core can be produced before a following stranding, even given systems that run at high speed and continuously and given systems with changing rotational sense of the stranding. A further goal of the invention was to implement an apparatus as initially set forth such that a complete and dependable enveloping of a central core can be produced in a fast and dependable way before a following stranding and such that it is suitable for very fast operation, i.e., fast and continuous throughput of the cable, even with changing rotational sense of the stranding.
For achieving the first object, the initially described method is characterized in that the material for the envelope is supplied in the form of a band with the same speed and, finally, is directed parallel to the core, such that at least two longitudinal structures that are essentially parallel to one another and to the longitudinal axis of the band and that reduce the flexural strength of the band are worked into the band, and such that the band, following the alignment parallel to the core and before the stranding, is automatically bent around the core at least twice at its longitudinal structures such that a closed sheath arises around the central core. Due to the equally fast delivery of the material for the envelope and the parallel alignment, the delivery speed need not be any higher than the throughput speed of the cable through the system, so that very high values thereof can be achieved. Working the longitudinal structures in, which reduces the risk of tearing, is thereby still possible in a relatively simple way. The two-time bending or, respectively, folding of the band in longitudinal direction yields a hollow profile structure, at least a structure with a triangular cross section of the material of the envelope that surrounds the core without gaping regions and, thus, dependably covers it on all sides and that is also not pressed open during the course of the following stranding.
It is provided according to a further feature of the invention that the longitudinal edges of the band lying opposite one another overlap after being bent around the core. The hold of the closed structure completely enveloping the core is thus improved further and a gaping thereof is prevented to the farthest-reaching extent.
The most dependable hold of the hollow structure composed of the structure folded or, respectively, bent around the central core in longitudinal direction is established when the overlapping longitudinal edges of the band are joined to one another at least at points. This can be achieved, for example, by gluing, punctiform as well, or by any other desired joining technique such as basting, sewing, clamping, etc.
The simplest processing for preserving a closed structure around the central core can be achieved in that at least two grooves are produced as longitudinal structures. The band can then be folded twice in the same direction in the region of these grooves, so that a hollow structure with a triangular cross section arises, which, given a corresponding arrangement of the grooves, can also be fashioned symmetrically with respect to its longitudinal axis.
It is advantageously provided according to a further feature of the invention that a plurality of grooves are produced on both sides of the band and the band is multiply folded, and that, during the course of bending the folded band around the core and the overlapping of the longitudinal edges, at least one groove of a longitudinal edge engages into a groove of the longitudinal edge lying opposite. A tighter wrapping of the central core with less unused cross section and, thus, a reduced need for material is thereby possible. Due to the plurality of grooves, the bending and, thus, the stressing of the material in the region of each and every groove is lower, so that a greater protection against damage is established, this being of particular significance given high-speed systems.
Given the aforementioned version of the method, an optimum protection against unwanted unraveling or gaping of the envelope can be achieved in that an overlap of a plurality of grooves is produced at each longitudinal edge. Of course, an at least punctiform, additional joining by gluing, basting, sewing or similar methods is thereby also advantageous and additionally enhances the durability of the envelope.
As provided in an advantageous version of the invention, grooves having a v-shaped cross section can be especially simply and easily formed.
It is provided according to a further feature of the invention that the envelope of the band-shaped material that surrounds the central core and is already closed is guided at essentially all sides between at least one location at which the completely closed configuration has been essentially achieved and the entry into a following stranding device. Particularly for high-speed stranding systems, maintaining the closed configuration and protection against subsequent changes are thus established.
For achieving the second object, the system for manufacturing ropes, cables or the like according to the present invention is characterized in that a guide roller oriented parallel to the moving direction of the core is provided for the band-shaped material, and that at least one tool is provided that works at least two parallel, longitudinal structures into the band at least one location at which the band lies on the guide roller. The guide roller allows an optimum guidance and alignment of the band and, due to the slight free length of the band from when it lifts off from the rollerxe2x80x94advantageously arranged close to the corexe2x80x94until the closed envelope has been finished, the risk of damage to or, respectively, tearing of the band is reduced to the farthest-reaching extent. This latter risk is also significantly reduced in that the tool for working the longitudinal structures in acts on the band where it is still lying against the guide roller and is thereby dependably guided and supported. The dependable guidance on the guide roller also increases the precision of the processing, then facilitates the following bending-over or folding to form the structure enveloping the core and the exact dimensioning of this structure.
Advantageously and according to a further feature of the invention, the circumferential surface of the guide roller in which the band lies is provided with at least one circumferential channel, and the tool is composed of at least one shaping roller pressed against the circumferential surface of the guide roller, the circumferential surface of said shaping roller being complementary to the circumferential channel in the guide roller.
In order to be able to produce a structure that can be easily bent around the core and that is nonetheless stable and durable, it is provided according to another feature of the invention, that the circumferential surface of the guide roller comprises at least two, preferably a plurality of circumferential grooves. The stressing of the band in the region of the individual grooves is correspondingly reduced, specifically given many grooves lying next to one another, and the following bending or folding in this region produces less stress on the material than given a very small number of grooves and a correspondingly greater bending of these few grooves.
A further distribution of the stressing of the material when shaping the grooves in the band-shaped material for the envelope can be achieved in that at least two shaping rollers are provided, each one thereof carrying a plurality of beads or burrs along its circumference that each respectively engage into a circumferential groove of the guide roller and that are fashioned complementary to these circumferential grooves, whereby the plurality and arrangement of the beads or burrs is selected such that each circumferential groove of the guide roller collaborates with at least one bead or burr. The stressing is thus also distributed along the path of the band on the guide roller and, thus, the risk of damage is reduced further.
The least possible stressing of the band and the greatest possible security against damage in the shaping of the grooves is established when each shaping roller is provided with only one bead or burr and a plurality of shaping rollers corresponding in number to the plurality of circumferential grooves in the guide roller and distributed over the circumferential region is provided, the band also lying on the guide roller via these.
A very simple and economically manufacturable device is characterized in that the circumferential grooves comprise a v-shaped cross section and the shaping rollers comprise corresponding beads with an angular cross section.
Advantageously, at least one guide means is also additionally provided, preferably in the form of a pipe that extends betweenxe2x80x94essentiallyxe2x80x94the location at which the envelope is essentially closed and the stranding means. As a result of this measure, it can be assuredxe2x80x94even given high-speed stranding systemsxe2x80x94that the arrangement composed of the core provided with the envelope and running at high speed is not damaged and that the configuration that is obtained does not subsequently change or open up again.